Rapid Accurate Evaluation of Prestress Losses


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Title: Rapid Accurate Evaluation of Prestress Losses

Author(s): A Ghali and W. H. Dilger

Publication: Journal Proceedings

Volume: 70

Issue: 11

Appears on pages(s): 759-763

Keywords: computer programs; creep properties; prestress loss; prestressed concrete; shrinkage; stresses; structural analysis; structural design.

Date: 11/1/1973

The difficulty in estimating accurately the losses due to creep, shrinkage, and relaxation of steel lies in: (a) prediction of coefficients related to the quality of concrete, steel, and the environment in which the structure will be like during the period of loss, (b) the interdependence of the amount of prestress loss produced by the three contributory causes. In practice the designer may recourse to result of tests or to recommended practice for values of cr eep shrinkage, and relaxation. Once these values are established the errors resulting from Item (b) above should be eliminated. This paper is written for this purpose. Using step-by-step procedure which accounts for elastic and creep recoveries of concrete and the effect of variation in stress level on the relaxation of steel, graphs are prepared for use in practice. The use of these allows economical design by accurate estimate of the loss in prestress without the necessity of performing the computations of the step-by-step procedure